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Removing Sn Cu Intermetallic from Semiconductors

Publishing Venue

IBM

Related People

Leff, J: AUTHOR

Abstract

This method permits the complete removal of Sn-Cu intermetallic without significantly damaging the underlying glass layer. In quality control product analysis, it is necessary to determine the effects of balling and chip joining on the protective glass layers of semiconductor devices. Conventionally, the metallurgy is removed by etching away the Sn-Pb portion in acetic acid and hydrogen peroxide, and the Cu-Sn intermetallic layer is readily soluble in HCl while the intermetallic layer is not.

Country

United States

Language

English (United States)

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Removing Sn Cu Intermetallic from Semiconductors

This method permits the complete removal of Sn-Cu intermetallic without
significantly damaging the underlying glass layer. In quality control product
analysis, it is necessary to determine the effects of balling and chip joining on the
protective glass layers of semiconductor devices. Conventionally, the metallurgy
is removed by etching away the Sn-Pb portion in acetic acid and hydrogen
peroxide, and the Cu-Sn intermetallic layer is readily soluble in HCl while the
intermetallic layer is not.

The prolonged etching in HCl, necessary to remove the intermetallic layer,
undermines the underlying glass layer and forms random cracks. This is
objectionable because it makes detection of glass damage due to balling and
joining difficult or impossible.

This method immerses the intermetallic layer in concentrated HNO(3) for
approximately 5 minutes, which converts it into a phase which is readily
removable with concentrated HCl. The subsequent exposure of the glass layer
to HCl is relatively short, on the order of 30 seconds. Such short exposure does
not significantly damage the underlying glass layer, thus permitting a thorough
inspection.